The present invention relates, in general, to electronic styli, and in particular, to a new and useful, non-marking, writing system which feels like an actual, physical writing instrument when used.
A pen-type computer input device which performs physical writing much like a ball-point pen on a writing surface, is disclosed by U.S. Pat. No. 5,159,321. A ball writing instrument is disclosed in this patent which leaves an ink mark on a writing surface as a ball rotates in its housing, in front of a reservoir of ink. In addition to leaving an ink mark, U.S. Pat. No. 5,159,321 discloses the use of a sensor for sensing the rotation of the ball. The rotation is used as an input to a computer, much like the rotation of a ball in a computer mouse is utilized to drive a cursor or otherwise convert movement of the mouse into location signals for the computer. Also see IBM Technical Disclosure Bulletin, Volume 16, No. 12, May 1974 which discloses a ball-point pen that includes accelerometers for detecting the movement of the writing instrument to record a pattern executed during a writing operation.
U.S. Pat. No. 4,034,155 discloses an electrical sensing writing pen which, in addition to executing a writing function, is used in conjunction with a writing surface to electronically detect and convey the position of the writing instrument on the writing surface for computer purposes.
Non-writing styli are also known which are used much the way a pen or pencil is used, but which leave no mark on a tablet or other computer equipment having a flat surface which is used with the stylus as an input device. Examples of these non-writing styluses can be found in U.S. Pat. Nos. 4,158,747 and 4,786,764 as well as 3,760,660; 3,707,098; 918,833 and 235,898. Styli for writing on a thick stack of carbon paper are also known which use a rolling ball in a housing. No ink is left by the ball but the ball is mounted in a lubricating housing or babbitt. See for example, U.S. Pat. Nos. 1,028,029; 1,171,146; 1,500,426; and 1,915,426. No effort is made in these structures to reproduce any particular writing feel but instead, a structure which can press much harder than normal writing pressure is provided. A computer stylus having a switch and a ball at the end without ink is also disclosed in U.S. Pat. No. 4,883,926. While the stylus is mentioned to have the proper "feel", as if the operator was using a pen or pencil, nothing in this reference suggests how this feel can be achieved.
In addition to computer input devices in the form of tablets, integral computer systems, known as personal digital assistance or PDA's, are known. These systems, exemplified by the Apple Newton Message Pad, include a wireless passive stylus which has a synthetic tip that is used like a writing instrument on an input panel of the device. The input panel is pressure sensitive and detects the instantaneous location of the synthetic tip, to record a virtual writing operation, such as the formation of letters and numbers, the creation of drawings, a signature and other writing operations which, if executed with a true physical writing instrument, will leave a mark, but which, in their electronic analogy, leave an electrically stored pathway to be reproduced on the writing surface, and which also is electronically stored. The pathway thus stored can either be subjected to character recognition software to determine whether the pattern contains identifiable symbols such as known numbers or letters, or can be stored simply as an image.
The A.T. Cross Company, assignee of the present application, has conducted subjective testing of existing desktop electronic digitizer tablets and PDA's and has demonstrated that using these tablets is less comfortable and less satisfying than conventional physical writing.
Quantitative testing by A.T. Cross Company has shown that existing virtual writing systems do not fall within a measured range of parameters which is found to be aesthetically satisfying and which characterizes physical writing.